<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>

  <link rel="stylesheet" href="./@rule.css">

</head>

<style>

.box {
  width: 200px;
  padding: 50px;
  border: 5px solid green;
}



</style>

<body>
  <div class="box">box</div>
  <div class="box content">content-box</div>
  <div class="box border">border-box</div>
  <div class="rotate"></div>
</body>
</html>